1. Field of the Invention
This invention relates generally to a distributor mountable frontally of a concrete screed, and to a screed assembly comprising such distributor.
2. Description of the Related Art
Applicant's prior U.S. Pat. No. 4,030,873 discloses a portable screed incorporating a motor-driven vibrating shaft within a light-weight open structural frame. A winching mechanism for a vibrating shaft type screed is described in applicant's prior U.S. Pat. No. 4,253,778.
Another type of screed employs a roller which is rotated in a direction opposite to the direction of travel and screeds concrete by moving the roller over freshly poured concrete in front of the roller. One such motor-driven screed roller is the Razor Back Roller Finisher sold by Allen Engineering Corporation of Paragould, Arkansas. A similar type of roller screed identified as the Hurricane screed is sold by C & S Manufacturing Company of Tulsa, Oklahoma.
The roller type screed has a number of advantages particularly in application to screeding concrete on slopes and grades, but has the disadvantage of not consolidating concrete as effectively as does a vibrating frame type screed.
In addition, when roller screeds are provided in extended lengths, above about 25 feet, deflection of the roller element is encountered, which adversely affects the profile of the concrete being screeded in many applications, or alternatively requires the fabrication of the roller element with a thick-walled structure to resist the deflection.
In an attempt to overcome the deficiencies of the roller type screeds while realizing the benefits associated with the vibrating frame type screeds, applicants' copending U.S. application Ser. No. 936,480 filed Nov. 26, 1986, entitled "Multi-Section Screed Roller Apparatus (now abandoned)," proposes an improved screed comprising an open multi-section frame on the front of which is mounted a motor-driven multi-section screed roller, and behind which is provided a pair of screed plates. On the rear of this screed is provided a driven vibrating shaft which extends lengthwise of the screed to induce vibration primarily in the trailing portions of the screed for consolidation of the concrete after it has been roughly screeded and graded by the multi-section roller. This apparatus further includes means for winching the screed in the direction of travel, and incorporates a turn buckle arrangement compensating for any tendency of the multi-section roller to deflect when the screed length is relatively long.
While the screed roller apparatus of the aforementioned application Ser. No. 936,480 incorporates a number of advantageous features of roller screeds and vibrating frame type screeds, in applications where very wet concrete is being screeded, the rough screeding, grading and distributing functions of the roller are not fully optimally achieved.
Another screed apparatus which has been commercially introduced is the Curl Edge Form concrete screed of AWS Manufacturing Inc. (Yorkville, Illinois). This screed features a frontal curl edge form wherein, the frontal screed blade is enclosed by a box-type assembly having a generally concavely formed frontal surface extending upwardly and forwardly from the box. This structure is said to provide increased concrete grading speed, whereby the concrete does not have to be graded as closely as would be the case in the absence of the curl edge form. The curl edge is said to curl the concrete forward during screeding to accomplish a more uniform finish, eliminating rollover of concrete, and improving forward speed.
U.S. patent application Ser. No. 006,508 filed Jan. 22, 1987 in the name of Donald R. Morrison (U.S. Pat. No. 4,722,638), discloses a concrete screed comprising an elongate frame with screed plates connected to its leading and trailing portions, and with a plow body mounted on the frame in close proximity to the leading screed plate. The plow body presents discrete surface portions including (i) a first generally horizontal surface portion extending forwardly from the vicinity of the first screed plate to a front leading edge and generally horizontally aligned with the first screed plate, and (ii) a second surface portion integrally joined to the front leading edge of the first surface portion and extending upwardly therefrom to an upper edge. Such plow body is highly beneficial in facilitating a high-speed, high-efficiency screeding operation, in which the applied concrete is directed by the plow body to the leading and trailing screed plates in succession, to achieve rapid application of a screeded surface to the concrete, and a high level of consolidation of the concrete in the screeding operation.
Although the various screeds described above are useful to varying degrees in achieving improvements in the screeding process, a particular problem in commercial screeding operations is the time and manpower typically required for redistributing the poured concrete before it is screeded. After the concrete is poured, workers with shovels or other implements are conventionally employed to redistribute the poured concrete, so that the wet concrete surface subsequently contacted by the screed is sufficiently level. If such manual leveling is not carried out, the concrete after screeding frequently exhibits "holes" where sufficient concrete was not provided, and/or "pile-up" of wet concrete occurs in which the piled concrete will either resist movement of the screed in its intended direction, or else "spill over" the top of the screed blade and thereby avoid the screeding process.
In an effort to reduce or eliminate the time, effort, and expense of manually leveling the poured concrete before screeding, screed designs have been proposed in which frontal distributors are provided on the screed to enhance the distribution and leveling of the concrete prior to contact with the active screeding surfaces.
One such device is the Allen Auger Paver.TM. manufactured by Allen Engineering Corporation, Paragould, Arkansas in which a spreading auger is mounted on the screed frame and reciprocated longitudinally thereof. The auger spreads the concrete and moves it forward, to minimize hand work, with the auger assembly automatically cycling at selected travel speeds. See also U.S. Pat. No. 4,466,757, assigned to the same company, which discloses a vibratory concrete screed with a concrete spreading device coupled to the screed frame to level the surface of the plastic concrete and distribute same in front of the screed blade. The spreading device includes a grading device having either an auger or a grading blade or both. The side-to-side translation of the grading device along with screed frame laterally distributes the excess concrete and displaces the concrete forward and away from the screed blade. The aforementioned auger-type screed systems, although representing an improvement in terms of eliminating manual labor in the distributing and leveling operation, is inherently limited to relatively low forward travel speeds, due to the necessity of accommodating the side-to-side movement of the bridge carrying the auger and/or grader means.
Accordingly, it is an object of the present invention to provide a distributor apparatus attachable to a screed, which provides a highly efficient distribution and leveling of freshly poured concrete for subsequent screeding, and which concurrently accommodates high speed forward travel of the screed across the concrete which is distributed and leveled by the distributor means.
It is another object of the present invention to provide a screed comprising such distributor, which is capable of high-speed screeding operation, while reducing or eliminating manual labor otherwise required to distribute and level the concrete prior to screeding thereof.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.